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blockservice.go
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blockservice.go
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// Package blockservice implements a BlockService interface that provides
// a single GetBlock/AddBlock interface that seamlessly retrieves data either
// locally or from a remote peer through the exchange.
package blockservice
import (
"context"
"io"
"sync"
"go.opentelemetry.io/otel/attribute"
"go.opentelemetry.io/otel/trace"
"github.com/ipfs/boxo/blockstore"
"github.com/ipfs/boxo/exchange"
"github.com/ipfs/boxo/verifcid"
blocks "github.com/ipfs/go-block-format"
"github.com/ipfs/go-cid"
ipld "github.com/ipfs/go-ipld-format"
logging "github.com/ipfs/go-log/v2"
"github.com/ipfs/boxo/blockservice/internal"
)
var logger = logging.Logger("blockservice")
// BlockGetter is the common interface shared between blockservice sessions and
// the blockservice.
type BlockGetter interface {
// GetBlock gets the requested block.
GetBlock(ctx context.Context, c cid.Cid) (blocks.Block, error)
// GetBlocks does a batch request for the given cids, returning blocks as
// they are found, in no particular order.
//
// It may not be able to find all requested blocks (or the context may
// be canceled). In that case, it will close the channel early. It is up
// to the consumer to detect this situation and keep track which blocks
// it has received and which it hasn't.
GetBlocks(ctx context.Context, ks []cid.Cid) <-chan blocks.Block
}
// BlockService is a hybrid block datastore. It stores data in a local
// datastore and may retrieve data from a remote Exchange.
// It uses an internal `datastore.Datastore` instance to store values.
type BlockService interface {
io.Closer
BlockGetter
// Blockstore returns a reference to the underlying blockstore
Blockstore() blockstore.Blockstore
// Exchange returns a reference to the underlying exchange (usually bitswap)
Exchange() exchange.Interface
// AddBlock puts a given block to the underlying datastore
AddBlock(ctx context.Context, o blocks.Block) error
// AddBlocks adds a slice of blocks at the same time using batching
// capabilities of the underlying datastore whenever possible.
AddBlocks(ctx context.Context, bs []blocks.Block) error
// DeleteBlock deletes the given block from the blockservice.
DeleteBlock(ctx context.Context, o cid.Cid) error
}
// BoundedBlockService is a Blockservice bounded via strict multihash Allowlist.
type BoundedBlockService interface {
BlockService
Allowlist() verifcid.Allowlist
}
var _ BoundedBlockService = (*blockService)(nil)
type blockService struct {
allowlist verifcid.Allowlist
blockstore blockstore.Blockstore
exchange exchange.Interface
// If checkFirst is true then first check that a block doesn't
// already exist to avoid republishing the block on the exchange.
checkFirst bool
}
type Option func(*blockService)
// WriteThrough disable cache checks for writes and make them go straight to
// the blockstore.
func WriteThrough() Option {
return func(bs *blockService) {
bs.checkFirst = false
}
}
// WithAllowlist sets a custom [verifcid.Allowlist] which will be used
func WithAllowlist(allowlist verifcid.Allowlist) Option {
return func(bs *blockService) {
bs.allowlist = allowlist
}
}
// New creates a BlockService with given datastore instance.
func New(bs blockstore.Blockstore, exchange exchange.Interface, opts ...Option) BlockService {
if exchange == nil {
logger.Debug("blockservice running in local (offline) mode.")
}
service := &blockService{
allowlist: verifcid.DefaultAllowlist,
blockstore: bs,
exchange: exchange,
checkFirst: true,
}
for _, opt := range opts {
opt(service)
}
return service
}
// Blockstore returns the blockstore behind this blockservice.
func (s *blockService) Blockstore() blockstore.Blockstore {
return s.blockstore
}
// Exchange returns the exchange behind this blockservice.
func (s *blockService) Exchange() exchange.Interface {
return s.exchange
}
func (s *blockService) Allowlist() verifcid.Allowlist {
return s.allowlist
}
// NewSession creates a new session that allows for
// controlled exchange of wantlists to decrease the bandwidth overhead.
// If the current exchange is a SessionExchange, a new exchange
// session will be created. Otherwise, the current exchange will be used
// directly.
// Sessions are lazily setup, this is cheap.
func NewSession(ctx context.Context, bs BlockService) *Session {
ses := grabSessionFromContext(ctx, bs)
if ses != nil {
return ses
}
return newSession(ctx, bs)
}
// newSession is like [NewSession] but it does not attempt to reuse session from the existing context.
func newSession(ctx context.Context, bs BlockService) *Session {
return &Session{bs: bs, sesctx: ctx}
}
// AddBlock adds a particular block to the service, Putting it into the datastore.
func (s *blockService) AddBlock(ctx context.Context, o blocks.Block) error {
ctx, span := internal.StartSpan(ctx, "blockService.AddBlock")
defer span.End()
c := o.Cid()
err := verifcid.ValidateCid(s.allowlist, c) // hash security
if err != nil {
return err
}
if s.checkFirst {
if has, err := s.blockstore.Has(ctx, c); has || err != nil {
return err
}
}
if err := s.blockstore.Put(ctx, o); err != nil {
return err
}
logger.Debugf("BlockService.BlockAdded %s", c)
if s.exchange != nil {
if err := s.exchange.NotifyNewBlocks(ctx, o); err != nil {
logger.Errorf("NotifyNewBlocks: %s", err.Error())
}
}
return nil
}
func (s *blockService) AddBlocks(ctx context.Context, bs []blocks.Block) error {
ctx, span := internal.StartSpan(ctx, "blockService.AddBlocks")
defer span.End()
// hash security
for _, b := range bs {
err := verifcid.ValidateCid(s.allowlist, b.Cid())
if err != nil {
return err
}
}
var toput []blocks.Block
if s.checkFirst {
toput = make([]blocks.Block, 0, len(bs))
for _, b := range bs {
has, err := s.blockstore.Has(ctx, b.Cid())
if err != nil {
return err
}
if !has {
toput = append(toput, b)
}
}
} else {
toput = bs
}
if len(toput) == 0 {
return nil
}
err := s.blockstore.PutMany(ctx, toput)
if err != nil {
return err
}
if s.exchange != nil {
logger.Debugf("BlockService.BlockAdded %d blocks", len(toput))
if err := s.exchange.NotifyNewBlocks(ctx, toput...); err != nil {
logger.Errorf("NotifyNewBlocks: %s", err.Error())
}
}
return nil
}
// GetBlock retrieves a particular block from the service,
// Getting it from the datastore using the key (hash).
func (s *blockService) GetBlock(ctx context.Context, c cid.Cid) (blocks.Block, error) {
if ses := grabSessionFromContext(ctx, s); ses != nil {
return ses.GetBlock(ctx, c)
}
ctx, span := internal.StartSpan(ctx, "blockService.GetBlock", trace.WithAttributes(attribute.Stringer("CID", c)))
defer span.End()
return getBlock(ctx, c, s, s.getExchangeFetcher)
}
// Look at what I have to do, no interface covariance :'(
func (s *blockService) getExchangeFetcher() exchange.Fetcher {
return s.exchange
}
func getBlock(ctx context.Context, c cid.Cid, bs BlockService, fetchFactory func() exchange.Fetcher) (blocks.Block, error) {
err := verifcid.ValidateCid(grabAllowlistFromBlockservice(bs), c) // hash security
if err != nil {
return nil, err
}
blockstore := bs.Blockstore()
block, err := blockstore.Get(ctx, c)
switch {
case err == nil:
return block, nil
case ipld.IsNotFound(err):
break
default:
return nil, err
}
fetch := fetchFactory() // lazily create session if needed
if fetch == nil {
logger.Debug("BlockService GetBlock: Not found")
return nil, err
}
logger.Debug("BlockService: Searching")
blk, err := fetch.GetBlock(ctx, c)
if err != nil {
return nil, err
}
// also write in the blockstore for caching, inform the exchange that the block is available
err = blockstore.Put(ctx, blk)
if err != nil {
return nil, err
}
if ex := bs.Exchange(); ex != nil {
err = ex.NotifyNewBlocks(ctx, blk)
if err != nil {
return nil, err
}
}
logger.Debugf("BlockService.BlockFetched %s", c)
return blk, nil
}
// GetBlocks gets a list of blocks asynchronously and returns through
// the returned channel.
// NB: No guarantees are made about order.
func (s *blockService) GetBlocks(ctx context.Context, ks []cid.Cid) <-chan blocks.Block {
if ses := grabSessionFromContext(ctx, s); ses != nil {
return ses.GetBlocks(ctx, ks)
}
ctx, span := internal.StartSpan(ctx, "blockService.GetBlocks")
defer span.End()
return getBlocks(ctx, ks, s, s.getExchangeFetcher)
}
func getBlocks(ctx context.Context, ks []cid.Cid, blockservice BlockService, fetchFactory func() exchange.Fetcher) <-chan blocks.Block {
out := make(chan blocks.Block)
go func() {
defer close(out)
allowlist := grabAllowlistFromBlockservice(blockservice)
var lastAllValidIndex int
var c cid.Cid
for lastAllValidIndex, c = range ks {
if err := verifcid.ValidateCid(allowlist, c); err != nil {
break
}
}
if lastAllValidIndex != len(ks) {
// can't shift in place because we don't want to clobber callers.
ks2 := make([]cid.Cid, lastAllValidIndex, len(ks))
copy(ks2, ks[:lastAllValidIndex]) // fast path for already filtered elements
for _, c := range ks[lastAllValidIndex:] { // don't rescan already scanned elements
// hash security
if err := verifcid.ValidateCid(allowlist, c); err == nil {
ks2 = append(ks2, c)
} else {
logger.Errorf("unsafe CID (%s) passed to blockService.GetBlocks: %s", c, err)
}
}
ks = ks2
}
bs := blockservice.Blockstore()
var misses []cid.Cid
for _, c := range ks {
hit, err := bs.Get(ctx, c)
if err != nil {
misses = append(misses, c)
continue
}
select {
case out <- hit:
case <-ctx.Done():
return
}
}
fetch := fetchFactory() // don't load exchange unless we have to
if len(misses) == 0 || fetch == nil {
return
}
rblocks, err := fetch.GetBlocks(ctx, misses)
if err != nil {
logger.Debugf("Error with GetBlocks: %s", err)
return
}
ex := blockservice.Exchange()
var cache [1]blocks.Block // preallocate once for all iterations
for {
var b blocks.Block
select {
case v, ok := <-rblocks:
if !ok {
return
}
b = v
case <-ctx.Done():
return
}
// write in the blockstore for caching
err = bs.Put(ctx, b)
if err != nil {
logger.Errorf("could not write blocks from the network to the blockstore: %s", err)
return
}
if ex != nil {
// inform the exchange that the blocks are available
cache[0] = b
err = ex.NotifyNewBlocks(ctx, cache[:]...)
if err != nil {
logger.Errorf("could not tell the exchange about new blocks: %s", err)
return
}
cache[0] = nil // early gc
}
select {
case out <- b:
case <-ctx.Done():
return
}
}
}()
return out
}
// DeleteBlock deletes a block in the blockservice from the datastore
func (s *blockService) DeleteBlock(ctx context.Context, c cid.Cid) error {
ctx, span := internal.StartSpan(ctx, "blockService.DeleteBlock", trace.WithAttributes(attribute.Stringer("CID", c)))
defer span.End()
err := s.blockstore.DeleteBlock(ctx, c)
if err == nil {
logger.Debugf("BlockService.BlockDeleted %s", c)
}
return err
}
func (s *blockService) Close() error {
logger.Debug("blockservice is shutting down...")
if s.exchange == nil {
return nil
}
return s.exchange.Close()
}
// Session is a helper type to provide higher level access to bitswap sessions
type Session struct {
createSession sync.Once
bs BlockService
ses exchange.Fetcher
sesctx context.Context
}
// grabSession is used to lazily create sessions.
func (s *Session) grabSession() exchange.Fetcher {
s.createSession.Do(func() {
defer func() {
s.sesctx = nil // early gc
}()
ex := s.bs.Exchange()
if ex == nil {
return
}
s.ses = ex // always fallback to non session fetches
sesEx, ok := ex.(exchange.SessionExchange)
if !ok {
return
}
s.ses = sesEx.NewSession(s.sesctx)
})
return s.ses
}
// GetBlock gets a block in the context of a request session
func (s *Session) GetBlock(ctx context.Context, c cid.Cid) (blocks.Block, error) {
ctx, span := internal.StartSpan(ctx, "Session.GetBlock", trace.WithAttributes(attribute.Stringer("CID", c)))
defer span.End()
return getBlock(ctx, c, s.bs, s.grabSession)
}
// GetBlocks gets blocks in the context of a request session
func (s *Session) GetBlocks(ctx context.Context, ks []cid.Cid) <-chan blocks.Block {
ctx, span := internal.StartSpan(ctx, "Session.GetBlocks")
defer span.End()
return getBlocks(ctx, ks, s.bs, s.grabSession)
}
var _ BlockGetter = (*Session)(nil)
// ContextWithSession is a helper which creates a context with an embded session,
// future calls to [BlockGetter.GetBlock], [BlockGetter.GetBlocks] and [NewSession] with the same [BlockService]
// will be redirected to this same session instead.
// Sessions are lazily setup, this is cheap.
// It wont make a new session if one exists already in the context.
func ContextWithSession(ctx context.Context, bs BlockService) context.Context {
if grabSessionFromContext(ctx, bs) != nil {
return ctx
}
return EmbedSessionInContext(ctx, newSession(ctx, bs))
}
// EmbedSessionInContext is like [ContextWithSession] but it allows to embed an existing session.
func EmbedSessionInContext(ctx context.Context, ses *Session) context.Context {
// use ses.bs as a key, so if multiple blockservices use embeded sessions it gets dispatched to the matching blockservice.
return context.WithValue(ctx, ses.bs, ses)
}
// grabSessionFromContext returns nil if the session was not found
// This is a private API on purposes, I dislike when consumers tradeoff compiletime typesafety with runtime typesafety,
// if this API is public it is too easy to forget to pass a [BlockService] or [Session] object around in your app.
// By having this private we allow consumers to follow the trace of where the blockservice is passed and used.
func grabSessionFromContext(ctx context.Context, bs BlockService) *Session {
s := ctx.Value(bs)
if s == nil {
return nil
}
ss, ok := s.(*Session)
if !ok {
// idk what to do here, that kinda sucks, giveup
return nil
}
return ss
}
// grabAllowlistFromBlockservice never returns nil
func grabAllowlistFromBlockservice(bs BlockService) verifcid.Allowlist {
if bbs, ok := bs.(BoundedBlockService); ok {
return bbs.Allowlist()
}
return verifcid.DefaultAllowlist
}